Understanding the Role of Mesoscale Atmosphere-Ocean Interactions in Seasonal-to-Decadal Climate Prediction

巧妙地预测年复一年的气候变化将具有巨大的价值，例如，提前发出干旱预警将有助于农民、水资源管理人员和救援机构应对水资源短缺的困难。气候变化在多大程度上是可预测的还不得而知，但厄尔尼诺现象的例子表明，可预测的变化可能来自大气和海洋之间的相互作用。最近的研究表明，与墨西哥湾流和黑潮流相关的大气-海洋耦合也可能导致可预测的气候变化。假设的耦合的一个关键方面是小空间尺度的参与，特别是大气对墨西哥湾流和黑潮暖水与周围冷水之间强烈而狭窄的温度对比的反应。与此同时，海洋对大气的反应可能涉及尖锐海洋锋面的中尺度动力学，表面风可以通过这些锋面诱导深层垂直运动。深层运动很重要，因为它们可以将大气与海洋中的水平联系起来，在海洋中，变化发生得很慢，从而创造了巧妙的长期预测的可能性。这里进行的研究利用以足够高的分辨率进行的气候模型模拟来探索与海-气耦合相关的可预测性的可能性，以捕捉这些机制。这项研究还着眼于高分辨率捕捉与气候变异性有关的极端天气的可能性，例如与厄尔尼诺事件有关的飓风和大气河流分布的变化。具体来说，首席调查人员(PI)使用共同体地球系统模型(CESM，1.3版)进行模拟，大气的网格间距为0.25度，海洋的网格间距为0.1度。这些模拟包括一个由10名成员组成的从1920年到2100年的未初始化的瞬变气候模拟，以及从1982年到2016年的一组追溯的5年气候预测。为探索小尺度机制的影响，采取了若干战略，例如在实验中，海洋模式产生的海表面温度在输入大气模式之前被平滑，从而使小尺度相互作用机制失效。如上所述，气候多变性的致命预测可能具有巨大的社会价值，从而努力确定气候系统在多大程度上实际上是可预测的，以及确定其可预测性的物理机制具有重大的更广泛的影响。该项目的更广泛影响还包括开放获取该项目中产生的模拟，这使得世界各地的研究人员能够从事气候系统可预测性的研究。私营部门还通过各种场所与研究界和公众进行接触，包括题为“在海洋上”的广播节目和国际CLIVAR暑期学校。更广泛的教育影响来自于PIs参与其部门的本科生研究体验计划，以及通过支持和培训一名博士后助理和一名研究生。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Skillful predictions of year-to-year climate variations would have tremendous value, for instance advanced warning of droughts would help farmers, water managers, and relief agencies cope with the hardships of water scarcity. The extent to which climate variations are predictable in general is not known, but the example of El Nino shows that predictable variations can arise from interactions between the atmosphere and the ocean. Recent research suggests that predictable climate variations could also result from atmosphere-ocean coupling associated with the Gulf Stream and the Kuroshio Current. A critical aspect of the hypothesized coupling is the involvement of small spatial scales, in particular the atmospheric response to the strong and narrow temperature contrasts between the warm waters of the Gulf Stream and Kuroshio currents and the surrounding cold water. Meanwhile the ocean's response to the atmosphere could involve the mesoscale dynamics of sharp ocean fronts, through which surface winds can induce deep vertical motions. Deep motions are important as they can connect the atmosphere with levels in the ocean where variability takes place slowly, thus creating the potential for skillful long-lead prediction.Research conducted here explores the potential for predictability associated with air-sea coupling using climate model simulations performed at high enough resolutions to capture the mechanisms. The research also looks at the potential for high resolution to capture the weather extremes associated with climate variability, for example changes in the distribution of hurricanes and atmospheric rivers associated with El Nino events. Specifically, the Principal Investigators (PIs) perform simulations using the Community Earth System Model (CESM, version 1.3) with 0.25 degree grid spacing for the atmosphere and 0.1 degree spacing for the ocean. The simulations include a 10-member ensemble of uninitialized transient climate simulations from 1920 to 2100, as well as an ensemble of retrospective 5-year climate predictions starting from years between 1982 and 2016. A number of strategies are pursued to explore the impact of small-scale mechanisms, such as experiments in which the sea surface temperatures produced by the ocean model are smoothed before they are fed into the atmospheric model, thereby disabling small-scale interaction mechanisms.Skillful predictions of climate variability could have tremendous societal value, as noted above, thus work to establish the extent to which the climate system is in fact predictable, and the physical mechanisms that determine its predictability, has substantial broader impacts. The broader impacts of the project are also served by open access to the simulations generated in the project, which allows researchers around the world to engage in research on climate system predictability. The PIs also engage in outreach to the research community and the general public through venues including a radio program titled "On the Ocean" and International CLIVAR summer schools. Educational broader impacts come from the PIs' participation in their department's Research Experiences for Undergraduates program, and through the support and training of a postdoctoral associate and a graduate student.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.